USB 3.0 standard wasn't meant to replace SATA. Thunderbolt has a better prospect though only very expensive computers and monitors and storage devices so far have Thunderbolt support.
Does anybody actually have and use 256GB USB 3.0 drives made of NAND? I have a 32GB USB 3.0 flash drive made of superior NAND chips with a brand name called 'AIO', but I paid nearly $99 for it. It's the fastest USB memory I ever tried, but any OCZ SSD I have is hundreds of times faster in terms of real world usage. The memory stick is not suitable for storing and playing MP3 files. I tried thousands of The Economist audiobook files on it, but it seemed taking forever as if it were Class 4 microSD on a smartphone.
Whenever Toshiba reduces its share of market shipment, that share will quickly go to SK Hynix or Micron. Samsung was the one actually hesitating NAND production during the recent two years. That's why it lost share to Toshiba though still is No. 1 with Toshiba rapidly catching up.
Several years ago, the market leaders of NAND were Intel and AMD. You can't find their names on the big five NAND manufacturer lists anymore because NAND is not profitable enough for them anymore. Intel's quickly exiting even from the venture with Micron while Micron sells only under one billion dollars of worth in a quarter - not big enough to make meaningful profits for Intel. Most of these NAND markets are OEM, manufacturers selling to other manufacturers, and brand names count little in the OEM market.